c# - Can move multiple items simultaneously in ListBox up the list, but not down? -

i have strange bug i'm having hard time figuring out.

if select multiple items in listbox , select arrow, items move 1 space if 1 unit. however, not happen when clicking down arrow move items down 1 spot each in list.

instead, if select number of items , click down arrow, none of items moves @ all, , if select odd number of items , click down arrow, bottom item moves down 1 space, while others stay are.

anyone have idea why might happening?

here code i'm using handle moving of items:

private void moveiteminselecteditemslistbox(object sender) {   if (selecteditemslistbox.selecteditems.count > 0)   {     // build list of items moved     list<object> listofitemstobemoved = new list<object>();      (int = 0; < selecteditemslistbox.selecteditems.count; i++)     {       listofitemstobemoved.add(selecteditemslistbox.selecteditems[i]);     }      (int k = 0; k < listofitemstobemoved.count; k++)     {       var selecteditem = listofitemstobemoved[k];       int selecteditemindex = selecteditemslistbox.items.indexof(selecteditem);       int numberofitemsinlist = selecteditemslistbox.items.count;        // if arrow clicked       if (sender.tostring().contains("▲"))       {         if (selecteditemindex == 0)         {           selecteditemslistbox.items.remove(selecteditem);           selecteditemslistbox.items.insert(numberofitemsinlist - 1, selecteditem);           selecteditemslistbox.setselected(numberofitemsinlist - 1, true);         }         else         {           selecteditemslistbox.items.remove(selecteditem);           selecteditemslistbox.items.insert(selecteditemindex - 1, selecteditem);           selecteditemslistbox.setselected(selecteditemindex - 1, true);         }       }       // if down arrow clicked       else if (sender.tostring().contains("▼"))       {         if (selecteditemindex == numberofitemsinlist - 1)         {           selecteditemslistbox.items.remove(selecteditem);           selecteditemslistbox.items.insert(0, selecteditem);           selecteditemslistbox.setselected(0, true);         }         else         {           selecteditemslistbox.items.remove(selecteditem);           selecteditemslistbox.items.insert(selecteditemindex + 1, selecteditem);           selecteditemslistbox.setselected(selecteditemindex + 1, true);         }       }     }   }  } 

it's problem direction of for loop: in essence, when moving items down, if moving up through list while checking items move down, end overlaps , other weird things. solution loop going down items if you're moving items down:

if (selecteditemslistbox.selecteditems.count > 0) {     list<object> itemstomove = (from object item in selecteditemslistbox.selecteditems select item).tolist();     int numitems = selecteditemslistbox.items.count;      // if arrow clicked     if (sender.tostring().contains("▲"))     {         (int = 0; < itemstomove.count; i++)         {             var selecteditem = itemstomove[i];             int oldindex = selecteditemslistbox.items.indexof(selecteditem);             int newindex = oldindex == 0 ? numitems - 1 : oldindex - 1;              selecteditemslistbox.items.remove(selecteditem);             selecteditemslistbox.items.insert(newindex, selecteditem);             selecteditemslistbox.setselected(newindex, true);         }     }     // if down arrow clicked     else if (sender.tostring().contains("▼"))     {         (int = itemstomove.count - 1; >= 0; i--)         {             var selecteditem = itemstomove[i];             int oldindex = selecteditemslistbox.items.indexof(selecteditem);             int newindex = oldindex == numitems - 1 ? 0 : oldindex + 1;              selecteditemslistbox.items.remove(selecteditem);             selecteditemslistbox.items.insert(newindex, selecteditem);             selecteditemslistbox.setselected(newindex, true);         }     } } 

(i took liberty of making of code smaller, e.g. changing variable names.)